U.S. patent number 10,388,549 [Application Number 15/347,519] was granted by the patent office on 2019-08-20 for on-board metrology (obm) design and implication in process tool.
This patent grant is currently assigned to APPLIED MATERIALS, INC.. The grantee listed for this patent is Applied Materials, Inc.. Invention is credited to Shekhar Athani, Rupankar Choudhury, Sandeep Kumpala, Hanish Kumar Panavalappil Kumarankutty, Khokan C. Paul, Jay D. Pinson, II, Hari K. Ponnekanti, Juan Carlos Rocha-Alvarez.
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United States Patent |
10,388,549 |
Paul , et al. |
August 20, 2019 |
On-board metrology (OBM) design and implication in process tool
Abstract
Implementations of the present disclosure generally relate to an
improved factory interface that is coupled to an on-board metrology
housing configured for measuring film properties of a substrate. In
one implementation, an apparatus comprises a factory interface, and
a metrology housing removably coupled to the factory interface
through a load port, the metrology housing comprises an on-board
metrology assembly for measuring properties of a substrate to be
transferred into the metrology housing.
Inventors: |
Paul; Khokan C. (Cupertino,
CA), Pinson, II; Jay D. (San Jose, CA), Rocha-Alvarez;
Juan Carlos (San Carlos, CA), Ponnekanti; Hari K. (San
Jose, CA), Choudhury; Rupankar (Bangalore, IN),
Athani; Shekhar (Bangalore, IN), Kumpala; Sandeep
(Bangalore, IN), Panavalappil Kumarankutty; Hanish
Kumar (Bangalore, IN) |
Applicant: |
Name |
City |
State |
Country |
Type |
Applied Materials, Inc. |
Santa Clara |
CA |
US |
|
|
Assignee: |
APPLIED MATERIALS, INC. (Santa
Clara, CA)
|
Family
ID: |
58721061 |
Appl.
No.: |
15/347,519 |
Filed: |
November 9, 2016 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20170148654 A1 |
May 25, 2017 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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62258894 |
Nov 23, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L
21/67775 (20130101); H01L 21/67196 (20130101); G05B
19/041 (20130101); H01L 21/68707 (20130101); H01L
21/67207 (20130101); H01L 21/67253 (20130101); G05B
19/401 (20130101); H01L 21/67201 (20130101); H01L
21/68764 (20130101); H01L 21/67724 (20130101); H01L
21/67389 (20130101); G05B 2219/40066 (20130101); G05B
2219/31459 (20130101) |
Current International
Class: |
H01L
21/67 (20060101); H01L 21/687 (20060101); H01L
21/673 (20060101); G05B 19/04 (20060101); G05B
19/401 (20060101); H01L 21/677 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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10-2015-0116332 |
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Oct 2015 |
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KR |
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201528416 |
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Jul 2015 |
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TW |
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201535575 |
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Sep 2015 |
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TW |
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Other References
International Search Report and Written Opinion of Related
application PCT/US2016/059944 dated Nov. 1, 2016. cited by
applicant .
Taiwan Application No. 105135825, Office Action and Search Report
dated Mar. 29, 2019, 8 pages. cited by applicant.
|
Primary Examiner: Hossain; Moazzam
Attorney, Agent or Firm: Patterson + Sheridan LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to U.S. provisional patent
application Ser. No. 62/258,894, filed Nov. 23, 2015, which is
herein incorporated by reference.
Claims
The invention claimed is:
1. An apparatus, comprising: a factory interface; a first storage
pod coupled to a first side of the factory interface through a
first load port, and the first storage pod comprises one or more
substrate carriers; a metrology housing removably coupled to the
first side of the factory interface through a second load port, the
metrology housing comprises an on-board metrology assembly for
measuring film properties of a substrate to be transferred into the
metrology housing, and the on-board metrology comprises an aligner
plate that is operable to rotate the substrate; and a load lock
chamber coupled to a second side of the factory interface and
operating at vacuum environment, wherein the factory interface has
a robot configured to provide access to the metrology housing and
the load lock chamber.
2. The apparatus of claim 1, wherein the on-board metrology
assembly comprises: a light source; a spectrograph; a supporting
frame securing the light source and the spectrograph; a first set
of fiber-optic bundles optically connected to the light source and
the spectrograph; and a first set of collimators coupled to the
first set of fiber-optic bundles.
3. An apparatus, comprising: a factory interface; a first storage
pod coupled to a first side of the factory interface through a
first load port, and the first storage pod comprises one or more
substrate carriers; a metrology housing removably coupled to the
first side of the factory interface through a second load port, the
metrology housing comprises an on-board metrology assembly for
measuring film properties of a substrate to be transferred into the
metrology housing; and a load lock chamber coupled to a second side
of the factory interface, wherein the second side is opposed to the
first side, and the factory interface has a robot configured to
provide access to the metrology housing and the load lock chamber,
wherein the on-board metrology assembly comprises: a light source;
a spectrograph; a supporting frame securing the light source and
the spectrograph; a first set of fiber-optic bundles optically
connected to the light source and the spectrograph; a first set of
collimators coupled to the first set of fiber-optic bundles; and an
aligner module, the aligner module comprising: an aligner plate
having a rotating mechanism; a second set of fiber-optic bundles in
electrical communication with the first set of fiber-optic bundles;
and a second set of collimators in electrical communication with
the first set of collimators, wherein the second set of fiber-optic
bundles is coupled to the second set of collimators.
4. The apparatus of claim 3, wherein the aligner module is disposed
on a mounting bracket, and the mounting bracket is supported by one
or more support brackets.
5. The apparatus of claim 4, wherein the one or more support
brackets are mounted onto a reference datum plate disposed on a
wall of the factory interface.
6. The apparatus of claim 5, wherein the support brackets are
connected to each other through a plate, and the plate having one
or more guiding pins.
7. The apparatus of claim 6, wherein the metrology housing has a
slot on a back side of the metrology housing to allow passage of
the one or more guiding pins.
8. The apparatus of claim 4, wherein the on-board metrology
assembly further comprising an adapter plate, wherein the second
set of collimators is mounted on the adapter plate.
9. The apparatus of claim 8, wherein a first collimator of the
second set of collimators is disposed at the center of the aligner
plate.
10. The apparatus of claim 9, wherein a second collimator, a third
collimator, a fourth collimator, and a fifth collimator of the
second set of collimators are disposed at locations corresponding
to four different radial regions of a substrate to be transferred
into the metrology housing.
11. The apparatus of claim 8, wherein the adapter plate is
supported by the aligner plate through a plurality of leveling
components configured to independently adjust horizontal leveling
of the adapter plate with respect to the mounting bracket.
12. A processing tool, comprising: a transfer chamber having a
robotic arm; a factory interface having an atmospheric robot,
wherein the factory interface further comprises: a reference datum
plate disposed on a wall of the factory interface on the second
side; and one or more support brackets mounted onto the reference
datum plate, the one or more support brackets have at least a
guiding pin; a batch curing chamber coupled to the factory
interface; a load lock chamber having a first side coupling to the
transfer chamber and a second side coupling to a first side of the
factory interface, the load lock chamber is configured to receive
one or more substrates from the atmospheric robot; a flowable CVD
deposition chamber coupled to the transfer chamber; a first storage
pod coupled to a second side of the factory interface through a
first load port, and the first storage pod comprises one or more
substrate carriers; and an metrology housing coupled to the second
side of the factory interface through a second load port, the
metrology housing comprises an on-board metrology assembly for
measuring film properties of a substrate to be transferred into the
metrology housing by the atmospheric robot.
13. The processing tool of claim 12, wherein the metrology housing
comprises a door disposed on a first side of the metrology housing
and a slot disposed on a second side of the metrology housing, the
second side opposing the first side, and the slot is sized to allow
passage of the guiding pin.
14. The processing tool of claim 12, wherein the on-board metrology
assembly comprises an aligner plate having a rotating mechanism,
and the rotating mechanism supports and rotates the substrate.
Description
FIELD
Implementations of the present disclosure generally relate to an
improved factory interface in a processing tool.
BACKGROUND
Plasma processing, such as plasma enhanced chemical vapor
deposition (PECVD), is used to deposit materials, such as blanket
dielectric films on substrates. In the PECVD film process, there
has been two aspects that impact overall throughput: 1) Long
chamber downtime after planned maintenance because iterative
process tuning, using standalone metrology, takes a long time
(typically over 18 hours); and 2) Tendency of film-thickness drift
with time that requires monitoring and tuning the process on a
regular basis. Thus, when using external standalone metrology, the
tuning process is time consuming and reduces the production time.
In order to increase production time, a procedure for reliable,
accurate and sustainable metrology integrated with the tool is
needed.
SUMMARY
Implementations of the present disclosure generally relate to an
improved factory interface that is coupled to an on-board metrology
housing configured for measuring film properties of a substrate. In
one implementation, an apparatus comprises a factory interface, and
a metrology housing removably coupled to the factory interface
through a load port, the metrology housing comprises an on-board
metrology assembly for measuring properties of a substrate to be
transferred into the metrology housing.
In another implementation, the apparatus includes a factory
interface, a first storage pod coupled to a first side of the
factory interface through a first load port, and the first storage
pod comprises one or more substrate carriers, a metrology housing
removably coupled to the first side of the factory interface
through a second load port, the metrology housing comprises an
on-board metrology assembly for measuring film properties of a
substrate to be transferred into the metrology housing, and a load
lock chamber coupled to a second side of the factory interface and
operating at vacuum environment, wherein the factory interface has
a robot configured to provide access to the metrology housing and
the load lock chamber.
In yet another implementation, a processing tool is provided. The
processing tool includes a transfer chamber having a robotic arm, a
factory interface having an atmospheric robot, a batch curing
chamber coupled to the factory interface, a load lock chamber
having a first side coupling to the transfer chamber and a second
side coupling to a first side of the factory interface, the load
lock chamber is configured to receive one or more substrates from
the atmospheric robot, a flowable CVD deposition chamber coupled to
the transfer chamber, a first storage pod coupled to a second side
of the factory interface through a first load port, and the first
storage pod comprises one or more substrate carriers, and an
metrology housing coupled to the second side of the factory
interface through a second load port, the metrology housing
comprises an on-board metrology assembly for measuring film
properties of a substrate to be transferred into the metrology
housing by the atmospheric robot.
BRIEF DESCRIPTION OF THE DRAWINGS
Implementations of the present disclosure, briefly summarized above
and discussed in greater detail below, can be understood by
reference to the illustrative implementations of the disclosure
depicted in the appended drawings. It is to be noted, however, that
the appended drawings illustrate only typical implementations of
this disclosure and are therefore not to be considered limiting of
its scope, for the disclosure may admit to other equally effective
implementations.
FIG. 1 illustrates a top plan view of an exemplary processing tool
that may be used to process a semiconductor substrate according to
implementations of the present disclosure.
FIG. 2 is a cross-sectional view of one implementation of a
flowable chemical vapor deposition chamber with partitioned plasma
generation regions.
FIG. 3 illustrates a flow diagram of one implementation of a
process 300 that may be performed in the processing tool.
FIG. 4A illustrates the in-situ metrology assembly in simplified
version according to implementations described herein.
FIG. 4B illustrates an enlarged view of a portion of the on-board
metrology assembly of FIG. 4A according to implementations
described herein.
FIG. 5A illustrates a cross-sectional view of an exemplary set up
of an on-board metrology assembly disposed in the on-board
metrology housing of FIG. 1.
FIG. 5B illustrates a perspective view of an aligner module of the
on-board metrology assembly according to one implementation of the
present disclosure.
FIG. 5C illustrates a cross-sectional view of the collimators
extending through a corresponding opening formed in an adapter
plate.
FIG. 5D illustrates a perspective view of an aligner plate having
an aligning mechanism.
FIG. 6A illustrates a perspective view of a wall of the factory
interface prior to engaging with the on-board metrology
housing.
FIG. 6B illustrates a perspective view of support brackets
according to one implementation of the present disclosure.
FIG. 6C illustrates a perspective view of an on-board metrology
housing showing the back side of the on-board metrology
housing.
To facilitate understanding, identical reference numerals have been
used, where possible, to designate identical elements that are
common to the figures. The figures are not drawn to scale and may
be simplified for clarity. It is contemplated that elements and
features of one implementation may be beneficially incorporated in
other implementations without further recitation.
DETAILED DESCRIPTION
Implementations of the present disclosure generally relate to an
improved factory interface that has an on-board metrology housing
coupled to a wall of the factory interface. The on-board metrology
housing has a metrology assembly configured to measure film
properties of a substrate. The factory interface has at least one
atmospheric robot configured to transfer substrates either between
the on-board metrology housing and a batch curing chamber coupled
to the factory interface, or between the on-board metrology housing
and a front opening unified pod (FOUR) coupled to the factory
interface.
Processing Tool
FIG. 1 illustrates a top plan view of an exemplary processing tool
100 that may be used to process a semiconductor substrate according
to implementations of the present disclosure. The processing tool
100 generally includes a factory interface 105, a batch curing
chamber 103, a transfer chamber 112, an atmospheric holding station
109, and a plurality of twin processing chambers 108a-b, 108c-d and
108e-f. The factory interface 105 is operating at atmospheric
pressure for storing and holding substrates. The factory interface
105 includes at least one atmospheric robot 104, such as a dual
blade atmospheric robot, and is configured to receive one or more
cassettes of substrates. On a first side of the factory interface
105, one or more load ports may be provided. In one exemplary
implementation, three load ports are provided. For clarity, only
two load ports 111, 113 are depicted in the implementation of FIG.
1. The load port 111, 113 is adapted to receive from a front
opening unified pod ("FOUR") 102 a substrate (e.g., 300 mm diameter
wafers) which is to be processed. The FOUR 102 has one or more
substrate carriers configured to temporarily and portably storing
the substrates. A load lock chamber 106 is coupled to a second side
(opposing to the first side) of the factory interface 105. The load
lock chamber 106 is coupled to the transfer chamber 112 in which
the plurality of twin processing chambers 108a-b, 108c-d and 108e-f
are located.
The substrate is transferred by the atmospheric robot 104 from the
FOUPs 102 to the load lock chamber 106. A second robotic arm 110 is
disposed in the transfer chamber 112 coupled to the load lock
chambers 106 to transport the substrates from the load lock
chambers 106 to processing chambers 108a-108f coupled to the
transfer chamber 112. The factory interface 105 therefore provides
a transition between the atmospheric environment of the factory
interface and the vacuum environment of the tool or processing
chambers.
The processing chambers 108a-108f may be any type of processing
chambers, for example, chemical vapor deposition (CVD) chambers,
atomic layer deposition (ALD) chambers, physical vapor deposition
(PVD) chambers, ion metal implant (IMP) chambers, plasma etching
chambers, annealing chambers, other furnace chambers, etc. In one
implementation, the processing chambers 108a-108f are configured
for depositing, annealing, curing and/or etching a flowable
dielectric film on a substrate. In one configuration, three pairs
of the processing chambers (e.g., 108a-108b, 108c-108d and
108e-108f) may be used to deposit the flowable dielectric material
on the substrate. If desired, any of these processing chambers
108a-b, 108c-d and 108e-f, or one or more additional processing
chambers may be coupled to the transfer chamber 112 and arranged to
perform other conventional semiconductor device fabrication process
such as oxidation, film deposition, etching, heating, degassing,
ashing, ion implanting, metrology, etc. upon application.
In some implementations, the batch curing chamber 103 is configured
to perform a batch curing process on multiple substrates
simultaneously that have the flowable dielectric material deposited
thereon. In such implementations, the batch curing chamber 103 is
generally configured to perform a curing process on the number of
substrates that can simultaneously undergo film deposition in the
twin processing chambers 108a-108b, 108c-108d and 108e-108f. Thus,
in the configuration illustrated in FIG. 1, the batch curing
chamber 103 is advantageously sized to accommodate six substrates
at one time during the curing process. Consequently, all substrates
that have been processed by the twin processing chambers 108a-108b,
108c-108d and 108e-108f can undergo the curing processing
simultaneously, thereby maximizing substrate throughput of the
processing tool 100.
Furthermore, in cases where multiple processing chambers have
different processing recipe start and end times, to prevent
substrates from remaining in the batch curing chamber 103 for
significantly different amounts of time, the processing tool 100
may include the atmospheric holding station 109 that is used to
hold the already processed substrates until the other subsequently
processed substrates are finished with their deposition processing.
The atmospheric holding station serves as a buffer station that
allows all of the substrates to be placed in the batch curing
chamber 103 at once. For example, the atmospheric holding station
109 is configured to temporarily store substrates outside the batch
curing chamber 103 until a desired number of substrates are
available for processing in the batch curing chamber 103. The
atmospheric robot 104 then loads the substrates into the batch
curing chamber 103 in quick succession, so that no film-deposited
substrate remains in the relatively high temperature batch curing
chamber 103 for more than a few seconds longer than any other
film-deposited substrate. Consequently, substrate-to-substrate
variation in the curing process can be minimized or reduced.
The batch curing chamber 103 may include a chamber body 103B and
slit valve 103A. The slit valve 103A is used to seal-off an
internal region of the chamber body 103B after substrates have been
positioned therein by the atmospheric robots 104.
In various implementations of the present disclosure, the factory
interface 105 has an on-board metrology housing 133 coupled to the
substrate existing side of the wall 107 adjacent to the FOUPs 102.
In one implementation as shown, the on-board metrology housing 133
is disposed between the pair of FOUPs 102. While two FOUPs 102 are
shown, it is contemplated that three or more FOUPs may be used to
correspond the load ports (such as load ports 111, 113). In one
example, three FOUPs are used, in which an additional FOUP is
disposed next to either side of the FOUP 102. The on-board
metrology housing 133 has an on-board metrology assembly 135
configured to measure film properties, such as film thickness, film
composition, sheet resistance, particle count, and film stress,
before and/or after processing of the substrate. In one
implementation, the on-board metrology assembly 135 is configured
to measure the film thickness of the substrate. The substrate to be
measured may be transferred from the load lock chambers 106 or any
of the FOUPs 102 to the on-board metrology housing 133 by the
atmospheric robots 104 through a load port 115 (disposed on the
substrate receiving side of the factory interface). Unlike the
conventional systems where the metrology assembly is provided at
the transfer chamber 112, the load lock chambers 106, the twin
processing chambers 108a-b, 108c-d and 108e-f, or in a separate
metrology chamber (not shown) coupled to the transfer chamber 112,
the factory interface 105 that is capable of measuring thickness of
films significantly shorter chamber downtime after planned
maintenance as the thickness can be measured immediately after the
process and can be used for process tuning through feedback
control. In addition, having the on-board metrology assembly 135
integrated onto the factory interface 105 provides easy access for
installation and/or servicing of the metrology assembly if needed.
Exemplary of the on-board metrology assembly 135 and its structural
relationship are further described with reference to FIGS. 4-6
below.
Flowable CVD Chamber and Deposition Process Examples
FIG. 2 is a cross-sectional view of one implementation of a
flowable chemical vapor deposition chamber 200 with partitioned
plasma generation regions. The process chamber 200 may be any of
the processing chambers 108a-f of processing tool 100 that are
configured at least for depositing a flowable dielectric material
on a substrate. In some implementations, rather than process
chamber 200, processing tool 100 may include any other suitable
chemical vapor deposition chamber.
During film deposition (e.g., silicon oxide, silicon nitride,
silicon oxynitride or silicon oxycarbide deposition), a process gas
may be flowed into a first plasma region 215 through a gas inlet
assembly 205. The process gas may be excited prior to entering the
first plasma region 215 within a remote plasma system (RPS) 201.
The process chamber 200 includes a lid 212 and showerhead 225. The
lid 212 is depicted with an applied AC voltage source and the
showerhead 225 is grounded, consistent with plasma generation in
the first plasma region 215. An insulating ring 220 is positioned
between the lid 212 and the showerhead 225, enabling a capacitively
coupled plasma (CCP) to be formed in the first plasma region 215.
The lid 212 and showerhead 225 are shown with an insulating ring
220 therebetween, which allows an AC potential to be applied to the
lid 212 relative to the showerhead 225.
The lid 212 may be a dual-source lid for use with a processing
chamber. Two distinct gas supply channels are visible within the
gas inlet assembly 205. A first channel 202 carries a gas that
passes through the remote plasma system (RPS) 201, while a second
channel 204 bypasses the RPS 201. The first channel 202 may be used
for the process gas and the second channel 204 may be used for a
treatment gas. The gases that flow into the first plasma region 215
may be dispersed by a baffle 206.
A fluid, such as a precursor, may be flowed into a second plasma
region 233 of the process chamber 200 through the showerhead 225.
Excited species derived from the precursor in the first plasma
region 215 travel through apertures 214 in the showerhead 225 and
react with the precursor flowing into the second plasma region 233
from the showerhead 225. Little or no plasma is present in the
second plasma region 233. Excited derivatives of the precursor
combine in the second plasma region 233 to form a flowable
dielectric material on the substrate. As the dielectric material
grows, more recently added material possesses a higher mobility
than underlying material. Mobility decreases as organic content is
reduced by evaporation. Gaps may be filled by the flowable
dielectric material using this technique without leaving
traditional densities of organic content within the dielectric
material after deposition is completed.
Exciting the precursor in the first plasma region 215 alone or in
combination with the remote plasma system (RPS) 201 provides
several benefits. The concentration of the excited species derived
from the precursor may be increased within the second plasma region
233 due to the plasma in the first plasma region 215. This increase
may result from the location of the plasma in the first plasma
region 215. The second plasma region 233 is located closer to the
first plasma region 215 than the remote plasma system (RPS) 201,
leaving less time for the excited species to leave excited states
through collisions with other gas molecules, walls of the chamber
and surfaces of the showerhead.
The uniformity of the concentration of the excited species derived
from the precursor may also be increased within the second plasma
region 233. This may result from the shape of the first plasma
region 215, which is more similar to the shape of the second plasma
region 233. Excited species created in the remote plasma system
(RPS) 201 travel greater distances in order to pass through
apertures 214 near the edges of the showerhead 225 relative to
species that pass through apertures 214 near the center of the
showerhead 225. The greater distance results in a reduced
excitation of the excited species and, for example, may result in a
slower growth rate near the edge of a substrate. Exciting the
precursor in the first plasma region 215 mitigates this
variation.
In addition to the precursors, there may be other gases introduced
at varied times for varied purposes. A treatment gas may be
introduced to remove unwanted species from the chamber walls, the
substrate, the deposited film and/or the film during deposition.
The treatment gas may comprise at least one of the gases from the
group comprising of H.sub.2, an H.sub.2/N.sub.2 mixture, NH.sub.3,
NH.sub.4OH, O.sub.3, O.sub.2, H.sub.2O.sub.2 and water vapor. A
treatment gas may be excited in a plasma and then used to reduce or
remove a residual organic content from the deposited film. In other
implementations, the treatment gas may be used without a plasma.
When the treatment gas includes water vapor, the delivery may be
achieved using a mass flow meter (MFM) and injection valve or by
other suitable water vapor generators.
In one implementation, the dielectric layer can be deposited by
introducing dielectric material precursors, e.g., a silicon
containing precursor, and reacting processing precursors in the
second plasma region 233. Examples of dielectric material
precursors are silicon-containing precursors including silane,
disilane, methylsilane, dimethylsilane, trimethylsilane,
tetramethylsilane, tetraethoxysilane (TEOS), triethoxysilane (TES),
octamethylcyclotetrasiloxane (OMCTS), tetramethyl-disiloxane
(TMDSO), tetramethylcyclotetrasiloxane (TMCTS),
tetramethyl-diethoxyl-disiloxane (TMDDSO),
dimethyl-dimethoxyl-silane (DMDMS) or combinations thereof.
Additional precursors for the deposition of silicon nitride include
SixNyHz-containing precursors, such as silyl-amine and its
derivatives including trisilylamine (TSA) and disilylamine (DSA),
SixNyHzOzz-containing precursors, SixNyHzClzz-containing
precursors, or combinations thereof.
Processing precursors include hydrogen-containing compounds,
oxygen-containing compounds, nitrogen-containing compounds, or
combinations thereof. Examples of suitable processing precursors
include one or more of compounds selected from the group comprising
of H.sub.2, a H.sub.2/N.sub.2 mixture, NH.sub.3, NH.sub.4OH,
O.sub.3, O.sub.2, H.sub.2O.sub.2, N.sub.2, N.sub.xH.sub.y compounds
including N.sub.2H.sub.4 vapor, NO, N.sub.2O, NO.sub.2, water
vapor, or combinations thereof. The processing precursors may be
plasma exited, such as in the RPS unit, to include N* and/or H*
and/or O*-containing radicals or plasma, for example, NH.sub.3,
NH.sub.2*, NH*, N*, H*, O*, N*O*, or combinations thereof. The
process precursors may alternatively, include one or more of the
precursors described herein.
The processing precursors may be plasma excited in the first plasma
region 215 to produce process gas plasma and radicals including N*
and/or H* and/or O* containing radicals or plasma, for example,
NH.sub.3, NH.sub.2*, NH*, N*, H*, O*, N*O*, or combinations
thereof. Alternatively, the processing precursors may already be in
a plasma state after passing through a remote plasma system prior
to introduction to the first plasma region 215.
The excited processing precursor 290 is then delivered to the
second plasma region 233 for reaction with the precursors though
apertures 214. Once in the processing volume, the processing
precursor may mix and react to deposit the dielectric
materials.
In one implementation, the flowable CVD process performed in the
process chamber 200 may deposit the dielectric materials as a
polysilazanes based silicon containing film (PSZ-like film), which
may be reflowable and fillable within trenches, features, vias, or
other apertures defined in a substrate where the polysilazanes
based silicon containing film is deposited.
In addition to the dielectric material precursors and processing
precursors, there may be other gases introduced at varied times for
varied purposes. A treatment gas may be introduced to remove
unwanted species from the chamber walls, the substrate, the
deposited film and/or the film during deposition, such as hydrogen,
carbon, and fluorine. A processing precursor and/or treatment gas
may comprise at least one of the gases from the group comprising
H.sub.2, a H.sub.2/N.sub.2 mixture, NH.sub.3, NH.sub.4OH, O.sub.3,
O.sub.2, H.sub.2O.sub.2, N.sub.2, N.sub.2H.sub.4 vapor, NO,
N.sub.2O, NO.sub.2, water vapor, or combinations thereof. A
treatment gas may be excited in a plasma and then used to reduce or
remove a residual organic content from the deposited film. In other
implementations the treatment gas may be used without a plasma. The
treatment gas may be introduced from into the first processing
region, either through the RPS unit or bypassing the RPS unit, and
may further be excited in the first plasma region.
Silicon nitrides materials include silicon nitride, SixNy,
hydrogen-containing silicon nitrides, SixNyHz, silicon oxynitrides,
including hydrogen-containing silicon oxynitrides, SixNyHzOzz, and
halogen-containing silicon nitrides, including chlorinated silicon
nitrides, SixNyHzClzz. The deposited dielectric material may then
be converted to a silicon oxide like material.
Processing Sequence Example
FIG. 3 is a flow diagram of one implementation of a process 300
that may be performed in the processing tool 100. The process
starts at block 302 where one or more substrates are transferred
from the pair of FOUPs 102 to the load lock chambers 106 by the
arms of an atmospheric robot 104.
At block 304, in some implementations where pre-calibration on
substrate is needed (for example to perform bare silicon substrate
calibration), before the substrates are transferred from the FOUPs
102 to the load lock chambers 106, the atmospheric robot 104 may
optionally move the substrates from the FOUPs 102 to the
atmospheric holding station 109 and then to the on-board metrology
housing 133 so that the film properties, such as film thickness
before any particular fabrication process(es) is rendered on the
substrate, are obtained. Once the desired film properties are
obtained, the substrates may be transferred from the on-board
metrology housing 133 to the load lock chambers 106 by the arms of
an atmospheric robot 104.
At block 306, once all the substrates or a desired number of
substrates are done with the measurement, the substrates are
transferred by the atmospheric robot 104 from the on-board
metrology housing 133 to the atmospheric holding station 109.
The substrate may be a silicon substrate having a layer or layers
formed thereon utilized to form a structure, such as a shallow
trench isolation (STI) structure. In one implementation, the
substrate is a silicon substrate having multiple layers, e.g., a
film stack, utilized to form different patterns and/or features.
The substrate may be a material such as crystalline silicon (e.g.,
Si<100> or Si<111>), silicon oxide, strained silicon,
silicon germanium, doped or undoped polysilicon, doped or undoped
silicon wafers and patterned or non-patterned wafers silicon on
insulator (SOI), carbon doped silicon oxides, silicon nitride,
doped silicon, germanium, gallium arsenide, glass, sapphire, metal
layers disposed on silicon and the like. The substrate may be any
of various shapes and dimensions, such as 200 mm, 300 mm or 450 mm
diameter wafers, or rectangular or square panels.
At block 308, the robotic arm 110 of the transfer chamber 112
optionally transfers the one or more substrates from the load lock
chambers 106 to the processing chambers 108a-108f for processing
the substrates, such as the flowable CVD process as described above
with respect to FIG. 2. In one implementation, the substrate is
transported to a deposition process chamber, such as the flowable
chemical vapor deposition (CVD) chamber 200 depicted in FIG. 2.
At block 310, once the substrates have been processed in the
processing chambers 108a-108f, the robotic arm 110 transfers the
processed substrates from the processing chambers 108a-108f to the
load lock chambers 106.
At block 312, the atmospheric robot 104 transfers the processed
substrates from the load lock chambers 106 to the atmospheric
holding station 109 until the other subsequently processed
substrates are finished with their deposition processing, or until
a desired number of substrates are available for processing in the
batch curing chamber 103. In one example, the processed substrates
are cooled and held in the atmospheric holding station 109 for
about 40 seconds to about 120 seconds, for example about 60
seconds.
At block 314, the atmospheric robot 104 moves the substrates from
the atmospheric holding station 109 to the batch curing chamber
103, so that no film-deposited substrate remains in the relatively
high temperature batch curing chamber 103 for more than a few
seconds longer than any other film-deposited substrate.
In cases where the substrate is deposited with a dielectric
material by the flowable chemical vapor deposition process, the
batch curing chamber 103 can cure and/or thermally process the
substrate to effectively remove moisture and other volatile
components from the deposited dielectric material to form a solid
phase dielectric material. As a result, a film formed via a
flowable CVD process can be converted to a dense, solid dielectric
film with little or no voids, even when formed on a substrate with
high aspect ratio features.
At block 316, the cured or thermally processed substrates are
transferred by the atmospheric robot 104 from the batch curing
chamber 103 to the atmospheric holding station 109 to cool the
substrates. In one example, the cured or thermally processed
substrates are held in the atmospheric holding station 109 for
about 40 seconds to about 120 seconds, for example about 60
seconds.
At block 318, the cured or thermally processed substrates are
transferred by the arms of an atmospheric robot 104 from the
atmospheric holding station 109 to the on-board metrology housing
133 coupled to the factory interface 105. The on-board metrology
assembly 135/500 in the on-board metrology housing 133 then
measures the film properties, such as film thickness of the
substrate.
At block 320, once all the substrates or a desired number of
substrates are done with the measurement, the substrates are
transferred by the atmospheric robot 104 from the on-board
metrology housing 133 to the atmospheric holding station 109.
At block 322, the atmospheric robot 104 moves the substrates from
the atmospheric holding station 109 to the load port of the pair of
FOUPs 102. The operations recited in blocks 302 to 322 may be
repeated until all the substrates in the FOUPs 102, or a desired
number of substrates in the FOUPs 102 are processed.
On-Board Metrology Assembly
FIG. 4A illustrates the in-situ metrology assembly in simplified
version according to implementations described herein. The on-board
metrology assembly 135 is a re-engineered design with similar
working principles. For simplicity, the in-situ metrology model is
used to describe the general aspects of the metrology hardware. The
on-board metrology assembly 135 generally includes a light source
424, fiber-optic bundles 426 and a spectrograph 428. The on-board
metrology assembly 135 also includes an aligner module 500, as will
be discussed below in FIGS. 5A and 5B.
The light source 424 and the spectrograph 428 are secured by a
supporting frame 402. The supporting frame 402 is supported by a
mounting bracket 450 (shown in FIG. 4B) that may be directly or
indirectly coupled to a wall 107 (shown in FIG. 1) of the factory
interface 105 and/or the on-board metrology housing 133 to improve
mechanical stability of the spectrograph 428 and the light source
424, which in turn improves signal stability. Each fiber-optic
bundle 426 may include one or more fiber-optic cables 429. Each
fiber-optic cable 429 may have an inside diameter of about 200
microns, which increases signal intensity and improves alignment
sensitivity when compared to fiber-optic cable having a smaller
inside diameter. With 200 micron fiber-optic cables, chromatic
signal drift is insignificant. It should be contemplated that even
though six fiber-optic bundles 426 are shown, more or less
fiber-optic bundles 426 may be used according to process
requirement.
In one implementation as shown, each fiber-optic bundle 426
includes two fiber-optic cables 429 each having an inside diameter
of about 200 microns, one for source signal (from light source 424
to the substrate) and one for receiving signal (reflected from the
substrate), which enables single point for maximum intensity and
ensures insensitivity of light injected into the fiber-optic cable
regardless of the locking orientation with the light source 424.
Some of the one or more fiber-optic bundles 426 may be optically
connected to the light source 424, and some of the one or more
fiber-optic bundles 426 may be optically connected to the
spectrograph 428. The on-board metrology assembly 135 may also
include a fiber-optic cable mount 404 that may be placed between
the first end and the second end. Each fiber-optic bundle 426 is
arranged to transmit light from the light source 424 towards a
measuring point on the substrate (not shown) at normal incidence.
The fiber-optic bundle 426 then captures reflection of the light
from the substrate at normal incidence and then transmits that
reflection towards the spectrograph 428. Each fiber-optic bundle
426 is coupled to a collimator 434 to collimate the light from the
light source 424 to illuminate about, for example, 2 mm in diameter
at the measuring point. In one implementation as shown, six
fiber-optic bundles 426 (i.e., fiber-optic bundles 426a-f, which
are better seen in FIG. 4B) are each coupled to a respective
collimator 434a-f. This configuration may be advantageous if two
processing chambers are used to share one light source and one
spectrograph. In such a case, each processing chamber may include
one processing region in which three fiber-optic bundles and three
collimators are used. While six collimators are shown in FIG. 4A,
it is contemplated that more or less collimators may be used
according to the configuration of the processing chamber and
process requirement.
The light source 424 may be a flash light source capable of
dispersing pulsed light at short durations. The light source 424
may be a white light source. In one implementation, the light
source 424 may be a Xenon flash-lamp. The light source 424 may
include a diffuser so the light generated is distributed
homogeneously through multiple fiber-optic bundles, such as the
fiber-optic bundles 426 and a reference fiber-optic bundle (not
shown). The reference fiber-optic bundle may be connected between
the light source 424 and the spectrograph 428 to provide a
reference channel to cancel out flash-to-flash variations or to
compensate any fluctuations/drifts overtime of the light source
424. The spectrograph 428 may include a charged-coupled device
(CCD) array light detector. In one implementation, the spectrograph
428 may measure unpolarized light with a wavelength range between
about 200 nm and about 2500 nm, such as between about 200 nm and
about 800 nm. In some implementations, the light source 424 may
produce ultraviolet (UV) light. In some implementations, light
source producing light having more deep ultraviolet (DUV) content
may be used. Examples of the light source for producing light
having more DUV content are plasma driven light sources or lasers.
In some implementation, light having wavelength in infrared range
(IR) may be used.
FIG. 4B illustrates an enlarged view of a portion of the on-board
metrology assembly 135 of FIG. 4A according to implementations
described herein. As shown in FIG. 4B, the light source 424 and the
spectrograph 428 are secured to the mounting bracket 450 by the
supporting frame 402 in order to improve mechanical stability of
the spectrograph 428 and the light source 424. A fiber SMA retainer
406 may be coupled to the spectrograph 428 for tightly retaining
the fiber-optic bundles 426 in order to improve signal stability.
Without the fiber SMA retainer 406, the fiber-optic bundles 426 are
vulnerable to be loosened due to tool vibration, manual touch and
other interferences. Similarly, a fiber SMA retainer 408 may be
coupled to the light source 424. Fiber SMA retainers 406, 408 on
the spectrograph 428 and the light source 424, respectively, help
improve signal stability. A fiber-optic cable mount 404 may be
disposed on the mounting bracket 450 for securing the fiber-optic
bundles 426 and the reference fiber-optic bundle 440. As shown in
FIG. 4B, there are six fiber-optic bundles 426a-f and one reference
fiber-optic bundle 426g coupled to the light source 424, and six
fiber-optic bundles 426a-f and one reference fiber-optic bundle
426g coupled to the spectrograph 428.
FIG. 5A illustrates a cross-sectional view of an exemplary set up
of an on-board metrology assembly 135 disposed in the on-board
metrology housing 133 of FIG. 1 according to one implementation of
the present disclosure. FIG. 5B illustrates a perspective view of
an aligner module 500 of the on-board metrology assembly 135
according to one implementation of the present disclosure.
The aligner module 500 generally includes collimators 534a-534e and
fiber-optic bundles 526a-526e. The aligner module 500 of the
on-board metrology assembly 135 is disposed on a mounting bracket
550. The mounting bracket 550 is supported by one or more rigid
support brackets 523 once the on-board metrology housing 133 is
engaged with the wall 107 of the factory interface 105. The one or
more rigid support brackets 523 are mounted onto a reference datum
plate 602 (see FIG. 6A) disposed on the wall 107 of the factory
interface 105. The casing of the on-board metrology housing 133 may
be perforated 527 for ventilation purposes. The aligner module 500
of the on-board metrology assembly 135 is disposed at a height
corresponding to the movement of the robot blade 104 to allow
transfer of the substrates in and out of the on-board metrology
housing 133 without interference with the collimators. Other parts
of the on-board metrology assembly 135, such as the light source
424, fiber-optic bundles 426 and the spectrograph 428 shown in
FIGS. 4A and 4B, may be positioned in a region below the mounting
bracket 550. Electronics for the on-board metrology assembly 135,
such as AC box, may also be positioned below the mounting bracket
550.
The on-board metrology housing 133 has a door 525 to allow access
and service of the on-board metrology assembly 135 and the
electronics. The on-board metrology assembly 135 and the aligner
module 500 are removable and can be horizontally slid into the
on-board metrology housing 133 using any suitable mechanism such as
a rack.
Referring now to FIG. 5B, the aligner module 500 may have a
supporting frame 502 disposed on the mounting bracket 550. The
aligner module 500 has an aligner plate 507 extending radially from
the bottom of the supporting frame 502. The aligner plate 507 has
its back side supported by a supporting block 580, which is mounted
to the mounting bracket 550. The mounting bracket 550 is supported
by one or more rigid support brackets 523 (see FIGS. 5A and 6B)
once the on-board metrology housing 133 is engaged with the wall
107 of the factory interface 105, as discussed above. The aligner
plate 507 has an aligning mechanism 509 for rotating a substrate
511. FIG. 5D illustrates a perspective view of the aligning
mechanism 509 disposed on the aligner plate 507. During operation,
the atmospheric robot 104 in the factory interface 105 picks up a
substrate from an atmospheric holding station and places it on the
aligning mechanism 509 within the on-board metrology housing 133.
The substrate 511 is then rotated by the aligning mechanism 509 to
allow thickness measurement on various points along the radii of
the substrate using the aligner module 500.
The aligner module 500 generally includes a plurality of
fiber-optic bundles 526a, 526b, 526c, 526d, and 526e and
collimators 534a, 534b, 534c, 534d, and 534e. Each of the
fiber-optic bundles 526a-526e is coupled to a corresponding
collimator 534a-534e, respectively. The collimators 534a-534e and
fiber-optic bundles 526a-526e are also in electrical communication
with the light source 424, fiber-optic bundles 426 and the
spectrograph 428 shown in FIG. 4A in order to transmit measurement
data. The collimators 534a, 534b, 534c, 534d, and 534e are mounted
on an adapter plate 503 at predetermined locations. In one
implementation as shown, the collimator 534b is disposed at the
center of the aligner plate 507 so that its sensor is focused at
the center of the substrate 511. The other four collimators 534a,
534c, 534d, and 534e may be disposed at locations corresponding to
four different radial regions of the substrate, for example, R
49.33 mm, R 98.67 mm, R 147 mm, and R 148 mm, to measure film
thickness at those positions. Different radii are contemplated,
depending on the process requirement and/or the size of the
substrate. The substrate can be rotated by any angle to measure
thickness of various points along the radii and thus to map for
film thickness on the substrate. In one implementation as shown,
the collimators 534b, 534c, and 534d are aligned along the radius
of the adapter plate 503. It is contemplated that more or less
collimators are contemplated. In one implementation, only four
collimators (selected from any of collimators 534a, 534b, 534c,
534d, and 534e) are used in the on-board metrology assembly
135.
The adapter plate 503 may be supported by the aligner plate 507
through a leveling stud/nut 508, 510, 512. The leveling stud/nut
508, 510, 512 can be any suitable mechanism, such as a spherical
bearing, for leveling the adapter plate. The leveling stud/nut 508,
510, 512 are configured to independently adjust vertical and/or
horizontal leveling of the adapter plate 503 with respect to
mounting bracket 550 at different locations. The adapter plate 503
may be leveled for parallelism with the mounting bracket 550 using
the leveling stud/nut 508, 510, and 512. Three point leveling
mechanism may be advantageous since there is no interference with
the robot blade, such as the atmospheric robot 104 shown in FIGS. 1
and 5A.
Each of the collimators 534a-534e may extend through a
corresponding opening 540 formed in the adapter plate 503, as shown
in FIG. 5C. The opening 540 may be slightly wider than the width of
the collimators 534 so the collimators can tolerate slight
misalignment when placing the collimators into the opening 540.
While not shown, an exhaust duct/channel with perforated sheets may
be provided inside the on-board metrology housing 133 so that
compressed air from the factory interface 105 enters and leaves the
on-board metrology housing 133 smoothly without recirculation. For
example, the exhaust duct/channel may be provided at locations near
the mounting bracket 550 and/or along the on-board metrology
housing 133. The exhaust duct/channel is provided such that a
laminar flow 582 is introduced from the factory interface 105 into
the on-board metrology housing 133. The laminar flow 582 is
maintained above the substrate 511 so that no particles are
accumulated on the substrate which can affect the measurement
and/or final chip. By maintaining laminar flow inside the on-board
metrology housing 133, any outgassing from the substrate 511 can be
exhausted, thereby preventing degradation of the collimators
534a-534e (FIG. 5B). The laminar flow 582 is then pumped out of the
on-board metrology housing 133 through a pump 584. It is
contemplated that the laminar flow 582 may include any suitable
inert gas, such as argon or helium.
For assembling the on-board metrology housing 133 with the factory
interface 105, a mechanism, such as the support brackets 523, can
be used to align the on-board metrology housing 133 precisely with
respect to the factory interface 105. The mechanism is capable of
locating the on-board metrology housing 133 onto the wall 107 with
same precision every time. FIG. 6A illustrates a perspective view
of the wall 107 of the factory interface 105 prior to engaging with
the on-board metrology housing 133. The wall 107 is provided with a
reference datum plate 602. The one or more rigid support brackets
523 are mounted onto the reference datum plate 602.
FIG. 6B illustrates a perspective view of the support brackets 523
according to one implementation of the present disclosure. The one
or more support brackets 523 may be connected to each other through
a plate 606. The plate 606 may have one or more pins 604 (only one
is shown) arranged to allow an operator to push the on-board
metrology housing 133 towards the factory interface 105 with a
desired precision. The support brackets 523 may also have two or
more aligning mechanisms 605 for holding the on-board metrology
housing 133 rigidly once it is engaged with the wall 107.
FIG. 6C illustrates a perspective view of the on-board metrology
housing 133 showing the back side. The back side (i.e., the side
facing the reference datum plate 602) of the on-board metrology
housing 133 may have one or more slots 608 (only one is shown) that
are sized to allow passage of the pin(s) 604. The on-board
metrology housing 133 may also have one or more mating locations
610 for receiving the aligning mechanisms 605 of the support
brackets 523, thereby assembling the on-board metrology assembly
135 with the wall 107 of the factory interface 105. The vertical
slots 608 and the mating locations 610 are provided to ensure ease
of assembly by one single operator. The on-board metrology housing
133 may also include three or more castor wheels 612 to prevent
rotation of the on-board metrology housing 133 about horizontal
axes while the operator is assembling and/or aligning the on-board
metrology housing 133 with the factory interface 105. If desired,
one or more leveling feet 614 may be disposed at the bottom of the
on-board metrology housing 133 to raise or lower the on-board
metrology housing 133. Once the on-board metrology housing 133 is
aligned and pushed by the operator, it rests against the support
brackets 523.
In operation, a robot blade (e.g., the atmospheric robot 104 shown
in FIG. 1) may move the substrate from the atmospheric holding
station 109 to the on-board metrology housing 133 containing the
on-board metrology assembly 500. The light source may be turned on
for about 60 seconds prior to stabilize the light signal from the
light source. Alternatively, the light source may be always on to
measure film thickness at times until the end of the thickness
measurement. The robot blade places the substrate onto the aligning
mechanism 509 where the substrate is rotated to find an alignment
marking, such as an alignment notch, on the substrate to allow the
substrate to be appropriately oriented within the on-board
metrology housing 133 and get ready for measurement. The term
orientation or orientation of the substrate refers to a rotational
position of the substrate about a central axis of symmetry of the
substrate.
Once the alignment marking is identified and the substrate is
stabilized, the pre-turned on light source distributes light
homogeneously through the fiber-optic cables to the fiber-optic
bundles 426a-426f and the fiber-optic bundle 526a-526e, and then to
the collimators 534a-534e to illuminate the substrate surface for
measurement. The fiber-optic cables collect reflected signal from
the substrate surface by collimating broadband light in the range
of 200-800 nm. During the operation for thickness measurement, the
substrate may be illuminated for about 1.5 seconds. The substrate
is then rotated by the aligning mechanism 509 counterclockwise or
clockwise to perform next measurement on the substrate. In one
implementation, six independent measurements are performed by
rotating the substrate 60.degree. for each measurement until a
360.degree. rotation of the substrate is completed. For substrate
stability, there may be a predetermined waiting period (based on
vibrational information and tool test) after each rotation and
before the next measurement is performed.
If desired, background signals may be collected for all collimators
for a period of time, such as about 10 seconds, to obtain an
averaged wavelength-dependent background signal per collimator. In
some implementations where the bare silicon substrate calibration
is desired, bare silicon substrate signals may be collected to
calibrate all collimator. The reflected signal from bare silicon
substrate may be collected for a period of time, such as about 30
seconds, in order to obtain an averaged wavelength-dependent signal
per collimator. This calibration can be extended to number of
rotation, corresponding to target substrate thickness rotation, for
each collimator, excluding the one at the center of the aligner
plate 507, in order to cancel out any potential error due to
wobbliness of the substrate with rotation. Based on known bare
silicon properties, reflectance of the target processed substrate
can then be measured and used for film thickness calculation. In
some implementations, the substrate at any of the FOUPs 102 (FIG.
1) can be transferred onto the aligning mechanism 509 within the
on-board metrology housing 133 to collect reflected signal and
measured thickness.
The collection of reflected signal and corresponding measurement of
thickness for a particular orientation of the substrate may
continue for a period of time, such as about 1.5 seconds for 15
data-points of thickness, in order to obtain an averaged thickness
of the film using either all data-points or desired number of
data-points for that particular location on wafer. The substrate
then may be rotated by any desired angle, such as 60 degrees, for
the thickness measurement on the next locations. Signal collection
and thickness measurement may be stopped for the period while the
target substrate rotates and stabilizes. The rotation of the target
substrate and measurement may be continued until the desired
numbers of rotation, such as 5 rotations, are completed and the
corresponding thicknesses are obtained. A film thickness map on the
substrate may be generated using the thickness measured through all
these rotations
Once the measurement is finished, the substrate is transferred by
the atmospheric robot 104 from the on-board metrology housing 133
back to the atmospheric holding station 109, and then to the load
port of the pair of FOUPs 102 (FIG. 1). This measurement procedure
may be repeated on the next substrate received in the on-board
metrology housing 133 until all or a desired number of substrates
are processed. Measurement and analysis of reflectance of the film
may be conducted simultaneously in a server where the thickness
information, film morphology, and/or other parameters of the film
are monitored in real time. The measurement data are analyzed to
determine if there is a system fault that causes the thickness
uniformity to drift. Once the fault is identified, the processing
tool can be set up to prevent further substrate processing until
the source(s) of fault is identified or corrected. The substrate is
then proceeded with the process using tuned conditions to tune
thickness uniformity.
The on-board metrology assemble 135 and the aligner module 500
reduce chromatic signal drift to the point that the resulting drift
of measured thickness is insignificant. The thickness drift for
continuous measurement using the on-board metrology assemble 135
and the aligner module 500 after deposition is almost negligible.
The on-board metrology assemble 135 and the aligner module 500 are
robust and are capable of measuring thickness with high accuracy
(sub-angstrom level).
While the foregoing is directed to implementations of the present
disclosure, other and further implementations of the disclosure may
be devised without departing from the basic scope thereof.
* * * * *